Gotham was under a cyber-attack by an unknown hacker, who left a riddle at every scene of their handiwork. Batman and Commissioner Gordon deduced the hacker to be Edward Nygma, aka The Riddler, and discovered that he was erasing

Careful vigilante, you know what they say, "Curiosity killed the Bat."

Synopsis for "What is Reality?"

Gotham was under a cyber-attack by an unknown hacker, who left a riddle at every scene of their handiwork. Batman and Commissioner Gordon deduced the hacker to be Edward Nygma, aka The Riddler, and discovered that he was erasing all of his personal and criminal records. Gordon received a message of a large crate painted with question marks delivered to the GCPD Headquarters. While Batman and Robin investigate the crate, Riddler's men infiltrate the Police Records Room and dispose of Edward Nygma's police record.

Batman, Gordon, and Robin discovered the crate to be a variation of the Chinese Box Puzzle. Robin managed to open the crate and it revealed a giant computer on the inside. Robin was assigned to study the computer while Batman headed to the Batcave to decipher Riddler's clues. With Alfred's help, Batman realized that the clues aren't in the answers, but the riddles themselves; specifically the numbers in the questions (500, 1000, 5). Batman converted the numbers into Roman Numeral which spells D,M, & V. Riddler is committing his next crime at the Department of Motor Vehicles. However, Batman arrived at the DMV too late to stop Riddler's men from destroying Nygma's driving records.

Meanwhile, Robin explored the computer's mainframe and found that it is a virtual reality simulator. He invites Gordon and shows him the program. But as Robin excused himself to get a snack, Riddler took control of the program and trapped Gordon's mind in the system. Batman was contacted by Riddler, who directed him back to the GCPD to find Gordon's situation. Riddler appeared on the computer's screen and explained to Batman and Robin that Gordon's life is in his hands and that even trying to unplug the system would be just as fatal. He demands that Batman solves his riddles inside the V.R. program in order to save Gordon's life. Batman accepted and entered the program with Robin providing help and advice.

After solving through the Riddler's challenges, which included secret doors, a chess game in which Batman played as a knight for his Dark Knight alias, and a constellation puzzle; Batman made it to the final challenge in which Riddler showed him a "Baxter's Puzzle Box" with Gordon trapped inside and is forcefully denied of any help from Robin. Fortunately, Batman realized that he can manipulate the virtual landscape like Riddler in which he duplicate himself to dismantling the box. Riddler respond by duplicating more of himself to stop Batman, but fell into Batman's trap since Riddler's consciousness was spread across his duplicates and he was unable to concentrate to maintain his virtual world, causing it to collapse. Batman rescued Gordon and both of them escaped the program.

Batman knew Riddler's location after judging from a clue left by Riddler: at the closed Gotham's World's Fair Exposition. He and Robin arrived there and found Riddler, who was unable to escape his program and his mind was indefinitely trapped there.

Notes

This is the 48th episode to be produced and the 45th to be aired.

Trivia

The chessboard stage of the virtual reality world was adapted into the second stage of the Riddler level in the Super Nintendo game The Adventures of Batman & Robin.

Only a few months after this episode aired, the "Knightfall" play on words was used as the name for the mainstream comics storyline that featured Bane breaking Batman's back and a temporary substitute taking up the mantle.

The idea of the Riddler leaving behind a numeric pattern hidden in the questions of past riddles was later used in the feature film Batman Forever.